To find the *exact* towing capacity for a specific 1988 C3500, you need to:
* Locate the owner's manual: This is the best source. The sticker inside the driver's side doorjamb might also provide some information, but the manual is more comprehensive.
* Check the data plate: The data plate (often on the driver's side doorjamb) will list the Gross Vehicle Weight Rating (GVWR), Gross Axle Weight Rating (GAWR), and other relevant information which can help determine the towing capacity.
* Consider the configuration: A truck with a gasoline engine will have a lower towing capacity than one with a diesel. Similarly, different axle ratios and transmission types affect towing ability.
Without knowing the specific configuration of your 1988 Chevy C3500, it's impossible to give a precise towing capacity. However, you can expect it to be in a range of 8,000 to 14,000 pounds or more, depending on the factors above. The higher end of that range is more likely for a dually (dual rear wheels) with a diesel engine.